Method and apparatus for adapting standard end cap assemblies of a perforating gun to function as tubing conveyed perforating end cap assemblies

ABSTRACT

Method and apparatus for adapting a Standard End Cap assembly of a perforating gun to function as a Tubing Conveyed Perforating end cap assembly of a perforating gun. The method includes inserting an inner end cap into an opening of a Standard End Cap, and positioning the inner end cap such that the inner end cap and Standard End Cap become interlocked without the need of a snap ring. The apparatus includes an inner end cap that may include anchors or receivers, and a Standard End Cap that may include anchors or receivers, such that the anchors in one component correspond to the receivers in the other component to facilitate the interlocking of the two components.

CLAIM OF PRIORITY

This utility application claims the benefit of U.S. Provisional PatentApplication No. 62/305,666, which was filed Mar. 9, 2016.

FIELD OF THE INVENTION

This invention relates to perforating guns and, more specifically, toadapting Standard End Cap assemblies of a perforating gun to function asa Tubing Conveyed Perforating end cap assembly of a perforating gun.

BACKGROUND OF THE INVENTION

Perforating guns are devices that are commonly used within the energyindustry in order to facilitate the extraction of energy resources fromthe ground. Energy resources, such as oil and natural gas, are generallyfound in underground reservoirs. In order to extract the oil or gas, adrill is often used to drill a long vertical hole from the groundsurface downward into the reservoir. By “tapping” the reservoir in thisway, the oil or natural gas contained in the reservoir can be brought tothe surface through the newly-made vertical hole using methods wellknown in the art.

Energy resource reservoirs, however, often span large horizontaldistances. A single reservoir may occupy many square acres or even manysquare miles of underground space. Reservoirs also occupy a certainvertical space underground; by way of example, the “top” of a reservoirmay be located two hundred (200) feet below the surface, but the“bottom” of the reservoir may be located eight hundred (800) feet belowthe surface. A drill that bores a vertical hole can access all “heights”of a reservoir; to extract oil or gas located deeper in the ground(i.e., more toward the reservoir's “bottom”), the person operating thedrill need only drill deeper.

But a single vertically drilled hole is only able to access a reservoirat one location relative to the reservoir's horizontal breadth. It isunfeasible to drill scores (or more) of vertical holes in order toaccess the entirety of a reservoir's horizontal breadth. One method ofaccessing a reservoir's horizontal breadth without drilling multiplevertical holes is to expand the subterranean portion of a vertical holein a horizontal direction. By expanding the subterranean portion of avertical hole in a horizontal direction, oil and gas located ahorizontal distance from the vertical hole can still be extractedthrough the vertical hole.

One method of expanding the subterranean portion of a vertical hole in ahorizontal direction is via a controlled subterranean explosion. Thecontrolled subterranean explosion displaces earth (such dirt, rock, orwhatever earthen material lines the vertically drilled hole), and bydoing so broadens the vertical hole horizontally.

Perforating guns are a device used to cause and control subterraneanexplosions to horizontally broaden vertical holes drilled to accessenergy resources. A drawing of a perforating gun is included herewith atReference No. 1 in FIG. 1. Perforating guns are typically cylindricaland contain strategically placed indentations known as “scallops.”Scallops are marked by Ref. No. 7 in FIG. 1. Some scallops in aperforating gun (but not necessarily all scallops) are “loaded” with acharge. A charge is explosive material that, as loaded, is positionedbelow a scallop. A charge situated in a perforating gun below a scallopcan be seen at Ref. No. 4 in FIG. 2. FIG. 3 shows a charge standingalone.

In order to accomplish the controlled subterranean explosion, one ormore perforating guns are lowered into the vertical hole that wasinitially drilled to tap the reservoir. When multiple perforating gunsare connected in an end-to-end manner and simultaneously lowered intothe same vertical hole, it is commonly known as a “string” ofperforating guns. There are a variety of well-known methods in the artfor lowering perforating guns into a vertical hole. When perforatingguns are lowered to the desired depth, the charges situated beneath thescallops are detonated.

Because the scallops are an indentation, the thickness of theperforating gun is less at a scallop than at unscalloped parts of theperforating gun. See FIG. 1, Ref. No. 7. As a result of the lesserthickness, when a charge below a scallop is detonated, the force of thedetonation from the charge is channeled through and expelled from thescallop. In this way, the indentations that form scallops serve as“holes” that are “punched out” when a charge located below the scallopis detonated (but to be clear, because the indentations that formscallops do not completely penetrate the walls of a perforating gun,scallops are not truly “holes” until the charges beneath the scallopsare detonated).

When the force of a charge detonated below a scallop is channeledthrough and expelled from the scallop, the channeled force displaces theearthen material located directly adjacent to the scallop, creatingfissures in the adjacent earthen material. A series of drawingsexemplifying the process by which perforating guns are lowered into avertical hole and then detonated to create fissures is included herewithas FIG. 16 and FIG. 17.

One variation of charge used in perforating guns contains an amount ofcopper situated atop the charge but below the scallop. When the chargeis detonated, the copper sitting atop is liquefied as a result of theheat generated by the detonation. In addition to liquefying the copper,the explosive force of the charge expels the molten copper through thescallop. When the molten copper is expelled through the scallop, itsfunction is tantamount to a liquid drill: the molten copper strikes theearthen material adjacent to the scallop from which it was expelled, andin doing so bores through the earthen material to create fissuresthrough which energy resources can flow.

Ensuring that perforating guns reach a desired depth and are able todetonate their charges are critical concerns when using perforating gunsto extract subterranean natural resources. End caps are devices situatedon the longitudinal ends of a perforating gun, and they impact themanner by which the perforating gun is lowered into a vertically drilledhole and the method by which perforating gun charges detonate. Becausethey affect the ability of a perforating gun to reach a desired depthand charge detonation, end caps are a critical component in anyperforating gun assembly.

The industry currently employs two types of end caps: Standard End Capsand Tubing Conveyed Perforating End Caps (“TCP End Caps”). Standard EndCaps permit strings of perforating guns to be hydraulically lowered intoa vertically drilled hole and utilize an electrical system to detonatecharges. A Standard End Cap can be seen in FIG. 11. The large opening inthe Standard End Cap denoted by Ref. No. 32 should be noted.

However, hydrostatic pressure naturally exists when vertical holes aredrilled to create wells. This hydrostatic pressure exerts a force upwardfrom within the well.

Because this force pushes upward, it opposes strings of perforating gunsthat are lowered downward into the well. As such, the force pushingdownward to lower a string of perforating guns into a well must be ableto overcome the hydrostatic force pushing upward opposing the loweringof the perforating guns, otherwise the string cannot be lowered into thewell. In the case of Standard End Caps, this means that the hydraulicforce used to lower a string into a well must be able to overcome thewell's natural hydrostatic force. This, however, is not always possible,which results in instances where perforating guns with Standard End Capscannot be lowered into a particular well because the available hydrauliclowering force is insufficient to overcome the well's hydrostatic force.

In instances where hydraulic force cannot overcome hydrostatic pressure,TCP End Caps must be used. Unlike assemblies employing Standard EndCaps, perforating gun assemblies that employ TCP End Caps aremechanically lowered into wells, rather than hydraulically. The methodsfor mechanically lowering TCP End Cap perforating gun assemblies arewell known in the industry. These mechanical methods are able to createmore force than hydraulic lowering methods, which allows TCP End Capperforating gun assemblies to be lowered through wells with highhydrostatic pressure where hydraulic lowering would be impossible. TCPEnd Cap assemblies also utilize a mechanical system to detonate thecharges, as opposed to the electrical system used with Standard End Capassemblies (both detonation systems are well known in the industry). ATCP End Cap can be seen in FIG. 12. It should be noted that the openingin the TCP End Cap, denoted by Ref. No. 33, is significantly smallerthan the opening in the Standard End Cap.

Because both Standard End Cap assemblies and TCP End Cap assemblies areused in the industry, it is advantageous to be able to adapt a StandardEnd Cap to function as a TCP End Cap if hydrostatic circumstances sorequire. A design currently exists that allows this type of adaptation:it is known as a “Snap Ring” assembly and is shown in FIG. 13. The SnapRing assembly works as follows:

-   -   By inserting an “inner end cap” 23 into the opening in a        Standard End Cap 21, one can adapt the Standard End Cap 21 to        function as a TCP End Cap.    -   However, the inner end cap 23 must fit snugly within the        Standard End Cap 21, because if the inner end cap 23 comes out        of place the Standard End Cap will no longer function as a TCP        End Cap.    -   To ensure the inner end cap 23 fits snugly within the Standard        End Cap's opening, the industry employs snap rings 22, which are        rings of metal.    -   Snap rings 22 are intended to surround the exterior        circumference of the inner end cap 23. By surrounding the outer        circumference of the inner end cap 23, the snap ring 22 occupies        any void that exists between the inner ring of a Standard End        Cap's opening and the outer circumference of an inner end cap        23. An example of such a void can be seen at Ref. No. 26 in FIG.        13.    -   By eliminating any void 26 between the Standard End Cap 21 and        the inner end cap 23, the snap ring 22 creates a snug fit that        holds the inner end cap 23 in place and allows the assembly to        function as a TCP End Cap.

Similar uses of end caps and snap rings in the manner described aboveare known in the prior art (see, e.g., U.S. Pat. No. 5,632,348; U.S.Pat. No. 6,009,947; U.S. Pat. No. 9,284,824). But problem with the useof snap rings 22 is that they require persons in the industry tomaintain a stock of three parts: the Standard End Caps 21, the inner endcaps 23, and the snap rings 22. The invention disclosed herein, whichApplicant was unable to locate in any prior art, permits a Standard EndCap to be adapted to function as a TCP End Cap utilizing only a StandardEnd Cap and an inner end cap.

SUMMARY OF THE INVENTION

The present invention provides a method for adapting a Standard End Capassembly into a TCP end cap assembly by employing an inner end cap thatincludes “anchors” and a Standard End Cap that includes “receivers.” Theinner end cap with anchors is placed into the opening of the StandardEnd Cap with receivers, then the inner end cap is rotated until theanchors on the inner end cap interlock with the receivers on theStandard End Cap, resulting in a snug fit that functions as a TCP endcap. The present invention also provides an alternative assembly,wherein the inner end cap includes receivers and the Standard End Capincludes anchors.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings included herewith are not intended to in any way limit thescope of the invention disclosed herein. The drawings are merelyincluded to clarify and exemplify the invention as disclosed and claimedherein.

FIG. 1 shows a standard perforating gun with standard circular-shapedscallops and a cross-sectional view of the same.

FIG. 2 shows a cross-sectional and standard view of a perforating gunwith charges loaded below circular scallops.

FIG. 3 shows a standard charge that may be loaded beneath a scallop in aperforating gun.

FIG. 4 shows a comparative view of a perforating gun with ellipticalshaped scallops and a perforating gun with circular shaped scallops.

FIG. 5 shows the milling of a scallop in a perforating gun using theindustry's current method, which does not create scallops ofsubstantially uniform thickness.

FIG. 6 shows a scallop created using the industry's current method.

FIG. 7 shows an example of the method of creating scallops ofsubstantially uniform thickness.

FIG. 8 shows a scallop created of substantially uniform thickness.

FIG. 9 shows a perforating gun that includes pliable arms to holdcharges in place and pliable tabs to hold primer cord in place.

FIG. 10 shows a string of perforating guns.

FIG. 11 shows a Standard End Cap assembly.

FIG. 12 shows a TCP end cap assembly.

FIG. 13 shows a snap ring assembly used to adapt a Standard End Cap intoa TCP end cap assembly.

FIG. 14 shows the present invention for adapting a Standard End Cap intoa TCP end cap assembly using an inner end cap with anchors and aStandard End Cap with receivers.

FIG. 15 shows an alternative version of the present invention foradapting a Standard End Cap into a TCP end cap assembly where the innerend cap includes receivers and the Standard End Cap includes anchors.

FIG. 16 shows generally how perforating guns are used to createsubterranean fissures that facilitate the extraction of energyresources.

FIG. 17 shows generally how perforating guns are used to createsubterranean fissures that facilitate the extraction of energyresources.

DETAILED DESCRIPTION OF THE INVENTION

The present invention comprises a two-piece assembly that allows a userto adapt a Standard End Cap into a TCP End Cap. Referring to FIG. 14,one embodiment of the present invention includes an inner end cap 15that includes anchors 14. As can be seen in FIG. 14, the anchors 14 arediscrete raised surfaces (such as a “bumps,” “wedges,” “arms,” etc.)that are included on the inner end cap. In the embodiment shown in FIG.14, the anchors 14 are included on the outer circumference 15 of theinner end cap. As also can be seen in FIG. 14, the inner ring of theStandard End Cap 3 includes “receivers” 20, which are indentations inthe Standard End Cap that correspond in shape and size to the anchors 14on the inner end cap. In the embodiment shown in FIG. 14, the receivers20 are included on the inner ring of the Standard End Cap 3.

The embodiment of the present invention shown in FIG. 14 works to securethe inner end cap 15 within the opening of the Standard End Cap 3 asfollows:

-   -   An inner end cap 15 with an anchor 14 is placed into the opening        of a Standard End Cap 3 with a receiver 20.    -   The inner end cap 15 is then rotated until the anchor 14 is        forced into the receiver 20.    -   When the anchor 14 is forced into the receiver 20, the inner end        cap 15 and the Standard End Cap 3 become interlocked, resulting        in a snug fit without needing an additional part in the form of        a snap ring.

It should be noted that, within the industry, inner end caps aremanufactured to fit relatively snugly within the opening of a StandardEnd Cap.

It should also be noted that the invention disclosed herein can functionby placing the anchor(s) on the Standard End Cap and the receiver(s) onthe inner end cap. FIG. 15 depicts this type of alternative assembly,where the inner end cap 29 includes a receiver 30 and the inner ring ofthe Standard End Cap includes an anchor 28. Thus, any configuration bywhich an inner end cap is held within the opening of a Standard End Capby creating a raised surface on one of the components that interlockswith a recessed portion on the other component, as such interlocking isdescribed herein, should be considered within the scope of the inventiondisclosed herein.

It should also be noted that multiple anchors and receivers may be usedin a single assembly. Thus, a single inner end cap or Standard End Capmay have one or more anchors intended to respectively interlock with oneor more receivers on a corresponding Standard End Cap or inner end cap.

Those with skill in the art will recognize that the anchors can be anyshape or size that can be included on the inner end cap or Standard EndCap and that can interlock with the receivers included on acorresponding Standard End Cap or inner end cap. Those with skill in theart will also recognize that receivers can be any shape or size that canbe included on the Standard End Cap or inner end cap and that caninterlock with the anchors included on a corresponding inner end cap orStandard End Cap. Thus, the essence of the invention is including oneither an inner end cap or a Standard End Cap any raised or recessedfeature that can interlock with a corresponding raised or recessedfeature on a corresponding Standard End Cap or inner end cap, so as tocreate a substantially voidless, snug fit between the inner end cap andthe Standard End Cap without needing an additional part in the form of asnap ring.

In addition, the anchors and receivers may be included, respectively, onother surfaces of the inner end cap and the Standard End Cap. The onlyrequirement of the present invention relative to the location of anchorsand receivers is that the anchors and receivers must be able to sync,such that the inner end cap and Standard End Cap form an interlocked,snug fit that results from the anchors interlocking with the receivers.

Having thus described the invention, what is desired to be protected byLetters Patent is presented in the subsequently appended claims.

What is claimed is:
 1. A method of adapting a Standard End Cap assemblyof a perforating gun to function as a Tubing Conveyed Perforating endcap assembly of a perforating gun, comprising: a) a Standard End Capthat includes at least one receiver; b) an inner end cap that includesat least one anchor; c) whereby the inner end cap is inserted into anopening of the Standard End Cap; and d) wherein the at least one anchoron the inner end cap interlocks with the at least one receiver on theStandard End Cap.
 2. The method of adapting a Standard End Cap assemblyof a perforating gun to function as a Tubing Conveyed Perforating endcap assembly of a perforating gun claimed in claim 1, wherein the atleast one receiver is included on the inner ring of the Standard End Capand the at least one anchor is included on the outer circumference ofthe inner end cap.
 3. A method of adapting a Standard End Cap assemblyof a perforating gun to function as a Tubing Conveyed Perforating endcap assembly of a perforating gun, comprising: a) an inner end cap thatincludes at least one receiver; b) a Standard End Cap that includes atleast one anchor; c) whereby the inner end cap is inserted into anopening of the Standard End Cap; and d) wherein the at least one anchoron the Standard End Cap interlocks with the at least one receiver on theinner end cap.
 4. The method of adapting a Standard End Cap assembly ofa perforating gun to function as a Tubing Conveyed Perforating end capassembly of a perforating gun claimed in claim 3, wherein the at leastone receiver is included on the outer circumference of the inner end capand the at least one anchor is included on the inner ring of theStandard End Cap.
 5. An apparatus for adapting a Standard End Capassembly of a perforating gun to function as a Tubing ConveyedPerforating end cap assembly of a perforating gun, comprising: a) aninner end cap; b) a Standard End Cap; and c) whereby the inner end capis able to interlock with the Standard End Cap when the inner end cap isinserted into an opening of the Standard End Cap.
 6. The apparatusclaimed in claim 5, wherein: a) the Standard End Cap includes at leastone receiver; and b) the inner end cap includes at least one anchor. 7.The apparatus claimed in claim 5, wherein: a) the Standard End Capincludes at least one anchor; and b) the inner end cap includes at leastone receiver.